1. Field of the Invention
The present invention relates to a torsion bar and, more particularly, to a torsion bar for use in raising a door lid.
2. Description of the Prior Art
Torsion bars have been used in assisting in the opening and raising doors and lids of vehicles. Typically, the torsion bar has at least two radially extending U-shaped portions. These portions are typically formed by bending the bar. When the door is open, one of the radially extending portions contacts the underside of the door and the other radially extending portion contacts the structure adjacent the door. When the door is closed, it pushes one of the radially extending portions towards the other, twisting the rod and creating a spring-like tension in the rod.
Japanese Publication 2875027 discloses a torsion bar formed to raise the engine cover of a forklift truck. The torsion bar has a door lid lifting portion extending radially outwardly from the bar adjacent each of a pair of hinges. A center portion extends in a radially opposite direction to abut the inside of the engine compartment. When the engine cover lid is closed, the door lid arm portions are twisted towards the center arm to create a torsion in the torsion bar acting in opposition to the closure. If the weight of the lid is greater than the biasing force of the torsion bar, the engine lid will remain in the closed position. When the engine cover is lifted to access the compartment, the biasing force of the torsion bar assists in raising the lid and holding the lid in the open position.
It is also known to use torsion bars to open trunk lids and hoods in automobiles. However, there are a number of parameters which are desirable in designing a door lifting mechanism. It is desirable to provide a xe2x80x9cpop-upxe2x80x9d force to raise the trunk lid a short distance from its locked position without any outside assistance. It is also desirable to provide a xe2x80x9chold openxe2x80x9d force which will support the door in any position where it is placed. It is desirable to have this force for use between the xe2x80x9cpop-upxe2x80x9d position and the approximately sufficient force to hold the door open in its fully extended position. In some cases, it is desirable that the torsion bar provide sufficient force to support in intermediate positions in between the pop-up position and the midway open position. Finally, the door should be forced to and held at the fully open position when raised by a person beyond the midway position. Thus, the torsion bar must have a large enough moment to open and support the door in this range of operation.
It has been difficult to find a good combination of all the variables to meet these design parameters. The length of typical torsion bars is such that these bars do not provide sufficient xe2x80x9chold openxe2x80x9d force to support the door at the intermediate positions. Accordingly, it is known to use a pair of torsion bars such as disclosed in Japanese Patent No. 55-94278. Each bar has a radially extending portion which is positioned against one of the hinge links. The torsion bars are then mounted to cross each other. However, such an installation is costly to build and install. Accordingly, it would be desirable to have a single torsion bar which met the necessary design parameters and reduces the mass and cost of production.
The invention relates to a torsion bar having an effective additional length. The effective additional length permits the torsion bar to produce a greater torsion bar moment without exceeding the design stress. The torsion bar includes a length extender portion disposed between a pair of radially extending lifting portions. In the preferred embodiment, the length extender portion is formed by bending a center portion of the rod into a shape. The shape will depend on the space available to accept the extender portion. In this way the effective length of the torsion bar is increased by the length of the extender portion thereby providing the desired xe2x80x9cpop openingxe2x80x9d force, xe2x80x9choldingxe2x80x9d force and moment to support the trunk lid in the xe2x80x9chold openxe2x80x9d position.